I haven't used LGI Secretabridge but I have used OL's Strength which is just laxo
In my experience oral Laxo needs to be run at higher doses to be effective(due to bio-availability issues), and my best results were dosing pre-workout. The range I found effective was 125-150mg pre-workout and 125mg on off days. So in short yes, LGI Secretabridge should work during a fasted state. That is how I ran oral laxo and how I would recommend running it.
As far as how long does it take for any given TD to fully absorb, that is an answer I cannot give you for various reasons. Unless there is a study done that illustrates the rate and peak of blood concentration of TD laxogenin per application, i would be just guessing and that does you no good. You're best bet is if you workout early in the morning, put TD laxo pre-bed after a shower or post workout(or both).
Does that help? Or is there something else you still are a bit curious about?